Thermosetting composition

ABSTRACT

The present invention provides a thermosetting composition which is excellent especially in storage stability and solid physical properties and can be used as automotive body sealers or undercoats. 
     The thermosetting composition according to the present invention comprises an acrylic plastisol consisting of a plasticizer having acrylic resin particles having a gradient-type structure in which the monomer unit proportion changes from the core to the shell multistep-wise or continuously and a filler dispersed therein and therewith formulated, as a thermosetting material, a blocked urethane prepolymer or blocked polyisocyanate compound and a latent curing agent therefor.

This is a nationalization of PCT/JP01/03120, filed May 16, 2000 andpublished in Japanese.

TECHNICAL FIELD

The present invention relates to a thermosetting composition, and moreparticularly a thermosetting composition which comprises an acrylicplastisol of acrylic resin particles having a gradient-type structurehaving a certain thermosetting material formulated therein and therebyhas enhanced storage stability and solid physical properties(elongation, strength) and is useful as, such as, automotive bodysealers or undercoats.

BACKGROUND ART

In the prior art, polyvinyl chloride (PVC) plastisols comprising aplasticizer having PVC particles dispersed therein have been utilized invarious fields, since they have excellent storage stability(particularly viscosity stability) and solid physical properties and anyplasticizer of which rarely bleeds. However, since a generation ofhydrogen chloride gas due to PVC at incinerating brings a destruction ofozon layer, a cause of acid rain, a cause of dioxin, etc., it has beengrowing strong that PVC plastisols are replaced by acrylic plastisolscomprising a plasticizer having acrylic resin particles and a fillerdispersed therein.

However, the prior acrylic plastisols are likely to be affected by thetype of plasticizer to be used and thus cannot be compatible withdevelopment of sufficient solid physical properties by heating gelationand storage stability (particularly viscosity stability) at paste state.Further, when a cheap and all-purpose plasticizer (e.g., diisononylphthalate) is used, the plasticizer may easily bleed since sufficientgelation cannot be obtained by heating, which may result in a surfacecontamination or inferior appearance.

So, there has been suggested an acrylic plastisol using acrylic resinparticles having a gradient-type structure, that is, in which themonomer unit proportion changes from the core to the shellmultistep-wise or continuously (gradient-type acrylic resin particles),which may prevent a plasticizer bleeding with sufficient solid(gelation) properties, even if an all-purpose plasticizer is used; andwhich aims at a progress of solid physical properties (see JapanesePatent Laid-Open Publication No. 295850/1996).

This acrylic plastisol using the gradient-type acrylic resin particlesbears comparison with the prior PVC plastisols in the points of solidphysical properties and prevention of a plasticizer bleeding aftergelation; and can be said to have fully a value as a replacement, but incase of supposing such as an application to a body sealer used for aconnecting part or gap part in automotive assembly line, it is necessaryto change the type of plasticizer and/or to increase the amount of thegradient-type acrylic resin particles in order to obtain sufficientlysatisfactory physical properties of sealant for attaining an originalair- and water-tight sealing, which may be deteriorated the storagestability and increased the viscosity, which be effected theworkability.

DISCLOSURE OF INVENTION

When the present inventors made intense studies for the purpose ofmodifying the physical properties of an acrylic plastisol using suchgradient-type acrylic resin particles, they found that if said acrylicplastisol is formulated with an polyisocyanate component wherein freeisocyanate group(s) (NCO) has been blocked and a latent curing agenttherefor as a thermosetting material, the physical properties of theirexpected objective are more improved without deterioration of storagestability, that is, the physical properties can be designed to toughstrength and excellent elongation and include excellent adhesion to apainted plate or a metal surface, and hence, they completed the presentinvention.

Thus, according to the present invention there is provided athermosetting composition which comprises an acrylic plastisolconsisting of a plasticizer having acrylic resin particles having agradient-type structure in which the monomer unit proportion changesfrom the core to the shell multistep-wise or continuously and a fillerdispersed therein and therewith formulated, as thermosetting material, ablocked urethane prepolymer wherein free NCO groups of a terminalNCO-containing urethane prepolymer have been blocked or a blockedpolyisocyanate compound and a latent curing agent therefor.

The above-described gradient-type acrylic resin particles in the presentinvention contain, as monomer unit, at least one selected from ethylmethacrylate, n-butyl methacrylate, i-butyl methacrylate, sec-butylmethacrylate, t-butyl methacrylate, ethylhexyl methacrylate, ethylacrylate, n-butyl acrylate, sec-butyl acrylate and t-butyl acrylate[hereinafter referred to as “A monomer”]; and a mixture of at least oneselected from methyl methacrylate and benzyl methacrylate with at leastone selected from methacrylic acid, acrylic acid, itaconic acid andcrotonic acid [hereinafter referred to as “mixture B monomer”]. Suchgradient-type acrylic resin particles can be produced by polymerizing Amonomer (described above) and mixture B monomer (also described above)while changing the ratio (proportion) of the former to the lattermultistep-wise or continuously. In this case, the proportion of Amonomer will be gradually reduced from the core toward the shell, whilethat of mixture B monomer will be gradually increased from the coretoward the shell. Typically, one may use an acrylic resin particlehaving an average molecular weight of 1,000-2,000,000 and a particlediameter of the primary particle and/or the secondary particle (whichconsists of aggregated primary particle) of 0.1-100 μm. For example,“DIANAL” which is commercially available from Mitsubishi Rayon Co., Ltd.is known.

Examples of filler in the present invention include, for example, clay,calcium carbonate (e.g., heavy-duty calcium carbonate, precipitatedcalcium carbonate, surface treated calcium carbonate, etc.), magnesiumcarbonate, titanium oxide, calcined plaster, barium sulfate, zinc white,silicic acid, mica powder, talc, bentonite, silica, glass powder, rediron oxide, carbon black, graphite powder, alumina, silas balloon,ceramic balloon, glass balloon, plastic balloon, metal powder, and thelike.

Examples of plasticizer in the present invention include, for example,phthalate ester such as di(2-ethylhexyl) phthalate, butyl benzylphthalate (high polar plasticizer), dinonyl phthalate, diisononylphthalate, diisodecyl phthalate, diundecyl phthalate, diheptylphthalate, butyl phthalyl butyl glycolate; aliphatic dibasic acid estersuch as dioctyl adipate, didecyl adipate, dioctyl sebacate; polyglycolbenzoate such as polyoxyethylene glycol dibenzoate, polyoxypropyleneglycol dibenzoate; trimellitate; pyromellitic acid ester; phosphatessuch as tributyl phosphate, tricresyl phosphate; hydrocarbons such asalkyl-substituted diphenyl, alkyl-substituted terphenyl, partiallyhydrogenated alkyl terphenyl, aromatic process oil, pine oil; and thelike. One or admixture of two or more selected from the group consistingof these plasticizers may be suitably selected and used depending on thetype of the gradient-type acrylic resin particle. Particularly,diisononylphthalate which is inexpensive and for all-purpose can beused.

Examples of blocked urethane prepolymer in the present invention can beprepared according to the following procedure:

i) First, polyol is allowed to react with an excess amount ofpolyisocyanate compound to obtain terminal NCO-containing urethaneprepolymer.

Examples of polyol include, for example, polyether polyol includingpolyoxyalkylene polyol (PPG), modified polyether polyol,polytetramethylene ether glycol; polyester polyol including condensationpolyester polyol, lactone polyester polyol, polycarbonate diol;polybutadiene polyol; polyolefin polyol; polymer polyol obtained bypolymerizing or graft-polymerizing acrylonitrile alone or a mixturemonomer of acrylonitrile with at least one selected from the groupconsisting of styrene, acrylamide, acrylic ester, methacrylic ester andvinyl acetate; and the like.

Examples of the above-described polyisocyanate compound includetrimethylene diisocyanate, tetramethylene diisocyanate, hexamethylenediisocyanate, pentamethylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, dodecamethylene diisocyanate,1,3-cyclopentane diisocyanate, 1,6-hexane diisocyanate (HDI),1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate,4,4′-methylene bis(cyclohexyl isocyanate), 4,4′-methylene bis(cyclohexylisocyanate), methyl 2,4-cyclohexane diisocyanate, methyl 2,6-cyclohexanediisocyanate, 1,4-bis(isocyanate methyl) cyclohexane, 1,3-bis(isocyanate methyl) cyclohexane, m-phenylene diisocyanate, p-phenylenediisocyanate, 4,4′-diphenyl diisocyanate, 1,5-naphthalene diisocyanate,4,4′-diphenyl methane diisocyanate (MDI), crude MDI, 2,4- or2,6-tolylene diisocyanate, 4,4′-toluidine diisocyanate, dianidinediisocyanate, 4,4′-diphenyl ether diisocyanate, 1,3- or 1,4-xylylenediisocyanate, ω, ω′-diisocyanate-1,4-diethylbenzene, etc.

ii) Next, the terminal NCO-containing urethane prepolymer is allowed toreact with a suitable blocking agent (typically at 0.9-1.5 equivalent ofthe blocking agent to 1 mol NCO of the former) for blocking free NCOgroups, thereby obtaining an objective blocked urethane prepolymer (itis particularly preferred to include said polymer polyol in at least onepart of said polyol).

Examples of blocking agent include, for example, alcohol such asmethanol, ethanol, propanol, butanol, isobutanol; phenols such asphenol, cresol, xylenol, p-nitrophenol, alkylphenol; active methylenecompounds such as methyl malonate, ethyl malonate, dimethyl malonate,diethyl malonate, ethyl acetoacetate, methyl acetoacetate,acetylacetone; acid amides such as acetamide, acrylamide, acetanilide;acid imide such as succinic acid imide, maleic acid imide; imidazolessuch as 2-ethyl imidazole, 2-ethyl-4-methyl imidazole; lactams such as2-pyrrolidone, ε-caprolactam; oximes of ketone or aldehyde such asacetoxime, methyl ethyl ketoxime, cyclohexanone oxime, acetaldoxime; andothers: ethyleneimine, bisulfite, etc.

A blocked polyisocyanate compound which may be used as polyisocyanatecomponent in place of the above-described blocked urethane prepolymer inthe present invention, can be obtained by blocking the free NCO groupsin the polyisocyanate compound exemplified in the preparation of saidterminal NCO-containing urethane prepolymer with said blocking agent.

The above-described gradient-type acrylic resin particles and theblocked urethane prepolymer or blocked polyisocyanate compound(polyisocyanate component) may be typically used at a weight ratio of20/1-1/20, and preferably 15/1-1/2. A smaller amount than the lowerlimit of the latter, polyisocyanate component may provide very littleadditional effect (improvement effect of elongation, strength), while alarger amount than the upper limit may effect workability.

Any latent curing agent can be used in the present invention which maybe activated at a temperature of 60° C. or higher (preferably 70-200°C.) to react with NCO, including, for example, dihydrazide compound suchas adipic acid dihydrazide, sebacic acid dihydrazide, isophthalic aciddihydrazide, 1,3-bis(hydrazino carboethyl)-5-isopropyl hydantoin,eicosane diacid dihydrazide, hydroquinone diglycolic acid dihydrazide,resorcinol diglycolic acid dihydrazide, 4,4′-ethylidene bisphenoldiglycolic acid dihydrazide; dicyandiamide; 4,4′-diamino diphenylsulfone; imidazole compounds such as imidazole, 2-n-heptane decylimidazole; melamine; benzoguanamine; N,N′-dialkyl urea compound;N,N′-dialkylthio urea compound; and polyamines which has a melting pointof 60° C. or higher and is present in a solid form at room temperature,such as diamino diphenylmethane, diamino biphenyl, diamino phenyl,phenylenediamine, tolylenediamine, dodecane diamine, decane diamine,octane diamine, tetradecane diamine, hexadecane diamine, hydrazidepolyamine.

In addition, one or more latent curing agents of the following groups(A), (B) and (C): can also be used.

(A) aliphatic polyamines such as ethylenediamine, diethylenetriamine,hexamethylenediamine, triethylenetetramine, polyoxypropylene amine;aromatic or cycloaliphatic polyamines such as m-xylylene diamine,hexamethylene tetramine, isophorone diamine; polyamine adduct such astriethanolamine, isopropanolamine, diethanolamine, diisopropanolamine,N,N,N′,N′-tetra (β-hydroxyethyl)ethyleneamine,N,N,N′,N′-tetra(β-hydroxypropyl)ethylenediamine,N,N,N′-tri(β-hydroxyethyl) ethylenediamine, N,N,N′-tri(β-hydroxypropyl)ethylenediamine, N,N′-di(β-hydroxyethyl) ethylenediamineN,N′-di(β-hydroxypropyl) ethylenediamine,N-(β-hydroxyethyl)ethylenediamine, N-(β-hydroxypropyl) ethylenediamine,N,N,N′,N′,N″-penta(β-hydroxypropyl) diethylenetriamine,N,N,N′,N′-tetra(β-hydroxypropyl) diethylenetriamine,N,N,N′-tri(β-hydroxypropyl) diethylenetriamine, N,N′-di(β-hydroxypropyl)diethylenetriamine, N-(β-hydroxypropyl) diethylenetriamine,N,N,N′,N′,N″,N″-hexa(β-hydroxypropyl) triethylenetetramine,N,N,N′,N′-tetra(β-hydroxypropyl) hexamethylenediamine, N,N′-di(β-hydroxypropyl) hexamethylenediamine,N,N,N′,N′-tetra(β-hydroxypropyl)-m-xylylenediamine,N,N′-di(β-hydroxypropyl)-m-xylylenediamine,N,N,N′,N′-tetra(β-hydroxypropyl) isophoronediamine,N,N,N′-tri(β-hydroxypropyl) isophoronediamine;3,9-bis(3-aminopropyl)-2,4,8,10-tetraoxaspiro[5.5]undecane compound;polyhydroxy compounds such as ethylene glycol, diethylene glycol,triethylene glycol, dipropylene glycol, glycerin, trimethylolpropane,1,4-butanediol, 1,6-hexanediol, 1,2,6-hexanetriol, pentaerythritol,diglycerin; and the like.

(B) polyamine modified compound, including:

reaction products of the following (a)-(c): (a) aliphatic polyamine(such as dimethylamino propylamine, diethylamino propylamine,dipropylamino propylamine, dibutylamino propylamine, dimethylaminoethylamine, diethylamino ethylamine, dipropylamino ethylamine,dibutylamino ethylamine, trimethyl hexamethylenediamine, diaminopropane,etc.); (b) a cyclic amine or aromatic polyamine which has at least oneNH₂ or NH group (for example, polyamines and monoamines such asmethaxylylenediamine, 1,3-bis (aminomethyl) cyclohexane, isophoronediamine, menthane diamine, diaminocyclohexane, phenylenediamine,toluylene diamine, xylylenediamine, diamino diphenylmethane, diaminodiphenyl sulfone, piperazine, N-aminoethyl piperazine, benzylamine,cyclohexylamine, etc.); and (c) diisocyanate compound (such asisophorone diisocyanate, methaxylylene diisocyanate, 1,3-bis (isocyanatemethyl) cyclohexane, 2,4-toluylene diisocyanate, 2,6-toluylenediisocyanate, 1,5-naphthylene diisocyanate, 1,4-phenylene diisocyanate,diphenylmethane-4,4′diisocyanate, 2,2′-dimethyldiphenylmethane-4,4′-diisocyanate, hexamethylene diisocyanate, trimethylhexamethylenediisocyanate, etc.) [wherein (a)=1 mole; (b)=0.02-3 moles;and (NH₂ and/or NH contained in (a) and (b))/(NCO contained in (c)) isequal to 1/1-1.2; and reaction may be performed in a solvent such asaromatic hydrocarbon, alcohol or ketone at from room temperature to 160°C.]; and

reaction products of said aliphatic polyamine (a), said amine (b) andepoxide compound (d) which includes glycidyl ether obtained by reactionof epichlorohydrin with polyhydric phenol (e.g., bisphenol A, bisphenolF, bisphenol S, hexahydrobisphenol A, catechol, resorcin,trihydroxybiphenyl, benzophenone, hydroquinone or tetramethylbisphenolA); polyglycidyl ether obtained by reaction of epichlorohydrin withaliphatic polyhydric alcohol (e.g., glycerin, neopentylglycol, ethyleneglycol or polyethylene glycol); glycidyl ether ester obtained byreaction of epichlorohydrin with hydroxy carboxylic acid (e.g., p-oxybenzoic acid or oxynaphthoic acid); polyglycidyl ester derived frompolycarboxylic acid such as phthalic acid, isophthalic acid,tetrahydrophthalic acid, endomethylene tetrahydrophthalic acid,trimellitic acid, polymerized fatty acid; glycidyl amino glycidyl etherderived from amino phenol or amino alkyl phenol; glycidyl amino glycidylester derived from aminobenzoic acid; glycidyl amine derived fromaniline, toluidine, tribromoaniline, xylylene diamine or 4,4′-diaminodiphenylmethane; and monoepoxide such as epoxidized polyolefin, glycidylhydantoin, glycidyl alkyl hydantoin, triglycidyl cyanurate, butylglycidyl ether, phenyl glycidyl ether, alkyl phenyl glycidyl ether,glycidyl benzoate ester, styrene oxide [wherein (a)=1 mole; (b)=0.5-5moles; and (NH₂ and/or NH contained in (a) and (b))/(epoxy groupcontained in (d)) is equal to 1/0.3-0.9, and (NH₂ and/or NH contained in(a) and (b))/(NCO contained in (c)) is equal to 1/0.15-1.35; first,portion or all of (b) and (d) are subjected to addition reactionoptionally in the above-described solvent at 60-120° C., and then (a),the reminder of (b), and (c) are added to react in the solvent at fromroom temperature to 160° C.]; and

(C) other polyamine modified compounds, including:

those obtained by allowing an addition product of an epoxy compound(e.g., bisphenol epoxy resin, novolac epoxy resin, polyester epoxy resinor polyether epoxy resin having one or more epoxy groups in themolecule) with one or more selected from the group consisting of theabove-described aliphatic polyamines, cyclic amines and aromaticpolyamines to react with a phenol compound (e.g., phenol resin or resolenovolac resin) and/or a polycarboxylic acid compound (e.g., adipic acid,sebacic acid, dodecanoic acid or azelaic acid) to mask the amino groupto inactivation [typically, 0.7-1.5 equivalent of epoxy group in theepoxy compound is used to one equivalent of amino group in the polyaminefor addition reaction, the resultant addition product (1 part by weight)is allowed to react with a phenol compound or polycarboxylic acidcompound (0.04-0.5 part by weight) to mask the active amino group; theresultant reaction product is inactive at a temperature under 60° C. andwill be activated at a temperature higher than 60° C., particularly 80°C. or higher].

Such a latent curing agent may be typically used at an amount of 1.0 to3.0 equivalent to NCO of the above-described polyisocyanate component.

The thermosetting composition according to the present invention mayconsist of a batch mixture system comprising the above-describedgradient-type acrylic resin particle, a filler, a plasticizer, anpolyisocyanate component and a latent curing agent at the predeterminedamounts. Optionally, a dehydrating agent (e.g., calcium oxide ormolecular sieves), thixotropic agent (e.g., organic bentonite, fumedsilica, aluminum stearate, metal soaps or castor oil derivatives), astabilizer [2,6-di-t-butyl-4-methylphenol, 2,2-methylene-bis(4-methyl-6-t-butylphenol) or dibutyldithiocarbamate nickel], a catalyst(e.g., dibutyltin dilaurate, lead octylate or bismuth octylate), asolvent (high boiling hydrocarbon solvent such as naphtha or paraffin),and/or an epoxy resin may be suitably selected and added.

BEST MODES FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in more detail inreference to the following Examples and Comparative Examples.

EXAMPLES 1 AND 2 AND COMPARATIVE EXAMPLES 1-5

(1) Preparation of Blocked Urethane Prepolymer No. 1

PPG (100 g) is allowed to react with MDI (27.8 g) and dibutyltindilaurate (0.008 g) at 80° C. for 5 hours (NCO/OH=2.2) to obtainterminal NCO-containing urethane prepolymer, which is then added withmethyl ethyl ketoxime (11.1 g) for reaction at 50° C. for 5 hours untilthe absence of NCO absorption is detected by IR. Then, a blockedurethane prepolymer is obtained. No. 2

Polymer polyol [“EL-920”, available from Asahi Glass Co., Ltd; obtainedby graft-polymerization of polyoxyalkylene ether polyol (molecularweight=4,900, f=3) and a mixture monomer of acrylonitrile andstyrene](100 g) is allowed to react with MDI (12.3 g) and dibutyltindilaurate (0.008 g) at 80° C. for 5 hours (NCO/OH=2.2) to obtainterminal NCO-containing urethane prepolymer which is then added withmethyl ethyl ketoxime (4.9 g) for reaction at 50° C. for 5 hours untilthe absence of NCO absorption is detected by IR. Then, a blockedurethane prepolymer is obtained.

(2) Preparation of Body Sealer

A body sealer is obtained by mixing the components listed in Table 1below under reduced pressure.

(3) Performance Test (Results are shown in Table 2 below)

i) Solid Physical Properties

The body sealer is coated on the substrate (coating thickness=2 mm) andbaked at 140° C. for 20 minutes. Dumbbell No. 2 is used to measureelongation (%) and tensile strength (kg/cm²) at a tension speed of 200mm/minute.

ii) Plasticizer Bleeding After Gelation

The body sealer is coated on the substrate and baked as described inabove i), and then left at 20° C. for 7 days. Bleeding of plasticizer isobserved by visual check: ◯indicates no bleeding; x indicates bleeding.

iii) Viscosity Stability

After 7-day storage at 40° C., % increase in the viscosity isdetermined.

iv) Adhesion

The body sealer is coated (coating size: 10×100×5 mm) on anelectrodeposition-coated plate (70×150×0.8 mm), baked at 140° C. for 20minutes, and left at 20° C. for 24 hours. The failure condition of thebody sealer is observed by peeling with a finger nail.

TABLE 1 Examples Comparative Examples 1 2 1 2 3 4 5 Gradient-type 112112 — — 112 135 — acrylic resin particle (*1) PVC (*2) — — 112 — — — —Acrylic resin — — — 112 — — 112 particle (*3) Calcium carbonate 100 100100 100 100 100 100 Surface treated  90  90  90  90  90  90  90 calciumcarbonate Diisononyl phthalate 150 150 150 150 150 150 150 Blockedurethane  10 — — — — —  10 prepolymer of (1), No. 1 Blocked urethane — 10 — — — — — prepolymer of (1), No. 2 Latent curing  1  1 — — — —  1agent (*4) Calcium oxide  5  5  5  5  5  5  5 Total 468 468 457 457 457480 468 (*1) “DIANAL RB2000” available from Mitsubishi Rayon Co., Ltd.,A monomer: n-butyl methacrylate, a mixture B monomer: methylmethacrylate/acrylic acid, particle diameter = 30 μm (*2) “PSH-180”available from Kaneka Corporation (*3) “F345” available from Zeon KaseiCo., Ltd., n-butyl methacrylate/methyl methacrylate copolymer (*4)“ADEKA Hardener EH 4070S”, polyamine modified compound available fromAsahi Denka Co., Ltd.

TABLE 2 Examples Comparative Examples 1 2 1 2 3 4 5 i) Solid physicalproperties Elongation 400 390 200 50  255 320 100 (%) Tensile  18  24 15 6  10  14  8 strength (kg/cm²) ii) ∘ ∘ ∘ x ∘ ∘ x PlasticizerBleeding after gelation iii) %  8  10 5 5  10  40  5 increase inviscosity iv) co- co- — — — — co- Adhesion hesive hesive hesive electro-failure failure failure deposition- coated plate

INDUSTRIAL APPLICABILITY

The thermosetting composition according to the present invention issufficiently adhesive to a coated surface or an electrodeposition-coatedsurface, and is particularly useful as a body sealer or an undercoatused in automotive assembly line. The inventive composition can also beused as a coating material or an adhesive material for various othermetal plates.

What is claimed is:
 1. A thermosetting composition which comprises anacrylic plastisol consisting of a plasticizer having acrylic resinparticles having a gradient-type structure in which the monomer unitproportion changes from the core to the shell multistep-wise orcontinuously and a filler dispersed therein and therewith formulated, asa thermosetting material, a blocked urethane prepolymer wherein freeisocyanate groups of a terminal isocyanate-containing urethaneprepolymer have been blocked or a blocked polyisocyanate compound and alatent curing agent therefor.
 2. The thermosetting composition accordingto claim 1 wherein as a thermosetting material, said blocked urethaneprepolymer and said latent curing agent therefor are formulated.
 3. Thethermosetting composition according to claim 2 wherein said blockedurethane prepolymer is a block form of a terminal isocyanate-containingurethane prepolymer obtained by reaction of polyol with an excess amountof polyisocyanate compound and a polymer polyol is included in at leastone part of said polyol.
 4. The thermosetting composition according toclaim 1 wherein said latent curing agent comprises a reaction product ofan aliphatic polyamine and a cyclic amine or aromatic polyamine havingat least one NH₂ or NH group and a diisocyanate compound.
 5. Thethermosetting composition according to claim 1 wherein said latentcuring agent comprises those obtained by allowing an addition product ofan epoxy compound and one or more selected from the group consisting ofaliphatic polyamine, cyclic amine and aromatic polyamine to react with aphenol compound and/or a polycarboxylic acid compound to mask the aminogroup to inactivation.
 6. The thermosetting composition according toclaim 1 wherein the ration by weight of said acrylic resin particlehaving a gradient-type structure to said blocked urethane prepolymer orblocked polyisocyanate compound is 20/1-1/20.